Abstract:

The method of Thallium - 201- single - photon emission computed tomography (Tl-201 SPECT) have been commonly used to detect uncontractile but viable myocardium in patients with ischemic left ventricular dysfunction. The aim of this study was to establish the value of nitrate echocardiography (NE) and low dose dobutamine echocardiography (LDDE) to detect viable myocardium when compared to Tl-201 SPECT. Twently patients (16 M, 4F; mean age: 56.4±9.6 years) who had anterior myocardial infarction in the last three months were studied. Within the same week, but on different days NE, LDDE and Tl-201 SPECT procedures were performed to the patients. In NE and LDDE procedures, patients were given 0.4-2 mg/kg/min. nitroglycerin and 5-10 mg/kg/min. dobutamine infusion, respectively. Evaluation of both the SPECT and the echocardiography (NE and LDDE) were done with sixteen-segment model. Regional thallium activity scores ranged from 0 (severe reduction in activity) to 3 (normal activity). At Tl-201 SPECT, on segments which have perfusion defect, identifying at least one degree of perfusion recovery, was evaluated as viability. At NE and LDDE, on segments which have two or more contiguous dysfunctional behaviour, determining at least one degree of wall motion recovery, was evaluated as viability. The wall motion score index (WMSI) was derived by summation of individual segment scores (1: normal; 4: dyskinetic) divided by the number of interpreted segments. Tl-201 SPECT showed a reversible defect in 91 (75%) segments among the 121 baseline echocardiographic dyssynergic segments. Improvement of both the SPECT and the LDDE were determinated in 70 (57%) segments. At both NE and LDDE, WMSI decreased according to baseline echocardiographic scrore index (p < 0.05). At baseline echocardiography, NE and LDDE, WMSI was 1.76±0.32, 1.58±0.33 and 1.56±0.30, respectively. When Tl-201 SPECT was taken as a gold standard, it was observed that at segments level, the sensivity of NE was 75% and specificity of it was 86%; the sensivity of LDDE was 76% and specificity of it was 80%. As a result, in determination of viable myocardium in patients with ischaemic left ventricular dysfunction, it was considered that NE and LDDE are as reliable as Tl-201 SPECT, easily appliable, and they can be preferred because they are much cheaper.

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